In the co-feature from Galen Center on the campus of USC in Los Angeles, Jermall Charlo (25-0, 19 KOs) retained his IBF Junior Middleweight World title with an emphatic fifth-round knockout over previously unbeaten, top-ranked Julian “J-Rock” Williams (22-1-1, 14 KOs).

Photo Credit: Stephanie Trapp/SHOWTIME®

Earlier in the day on SHOWTIME, unbeaten IBF Heavyweight World Champion Anthony Joshua (18-0, 18 KOs) knocked out Eric Molina (25-4, 19 KOs), of Weslaco, Texas, in the third round in Manchester, England.

Mares, of Huntington Beach, Calif., by way of Guadalajara, Mexico, was victorious by the scores of 117-110, 116-111 and 112-115. Judge Kermit Bayless was the lone descender to score the hard-fought match for the Argentine. Mares scored the bout’s lone knockdown in the 11th round. Cuellar, of Buenos Aires, had an 11-fight winning streak end.

Mares, making his first start in 16 months and first with renowned trainer Robert Garcia, executed a technically sound game plan and was the more accurate puncher than Cuellar, who was under the tutelage of Hall of Famer Freddie Roach for the first time in his career.

“I feel so good, it’s been a long time. I’m champion, baby,’’ said Mares, 31, a former WBC featherweight and super bantamweight world champion and IBF bantamweight world champion, who became Garcia’s 10th world champion. “We had the perfect game plan.

“I never doubted myself. I felt it in my heart. When I fought Leo (Santa Cruz) I beat myself because I fought the wrong fight. I fought smart tonight. I thought it would be a unanimous decision, but at the end of the day I’m champion.’’

Cuellar is known as a devastating puncher, but he was unable to land his power shots or cut off the ring against Mares, who seemingly pocketed rounds with accuracy and a solid left hook. Mares floored Cuellar with a straight right in the opening minute of the 11th, sending Cuellar to the canvas for the third time of his career. The onslaught continued, with a resurgent Mares teeing off on Cuellar until he raised his hands following the final bell.

“They said he was a power puncher, they said he was going to knock me out, but I proved that I have some power, too,’’ said Mares, who dropped a majority 12-round decision to Santa Cruz in his last fight on Aug. 29, 2015. “I want Leo, I want (Carl) Frampton, I want anyone. I’m a champion. I’m not afraid of anyone.”

Cuellar stated his case for a rematch afterward.

“I thought the fight was pretty even until he threw me down, and that’s when he took control,” said Cuellar, who was making his third title defense. “He definitely had the boxing skills going today. I would have preferred a rough fight, but Mares had his skills today. I want a rematch. I gave him the opportunity and now I think it’s fair that he gives it to me.”

In one off the fights streamed earlier Saturday on FACEBOOK LIVE, Sergey Lipinets (11-0, 9 KOs) knocked out Lenny Zappavigna (35-3, 25 KOs) to become the mandatory challenger for the IBF Junior Welterweight World Title.

After flooring Zappavigna midway through the fourth, Lipinets finished off the Australian with an overhand right in the eighth in a closely contested and bloody affair.

“Yes, this was my toughest fight, it’s bloody and rugged but no problem for me,’’ Lipinets said. “This was an eliminator and now I want my next fight to be for the world championship. Julius Indogo has the IBF title and now I’m the mandatory.

“I’m very happy with my performance. We’ve worked on adjusting during fights and that worked very well for me tonight. I was hoping for the knockout but my trainer said to keep working and the stoppage will come.”

“I left it all in the ring,’’ Zappavigna said. “I fought my heart out and I came here to give it my best. Even though I’m disappointed with the loss, I am at peace with the result because I know I couldn’t have done anything else.

“I wish Sergey all the best in his world title fight.

“I know my fans are behind me and I’m bringing pride back to Australia. I know I was in control of the fight, but my Australian ‘white line fever’ kicked in and I tried to take his head off.”

“He was a little awkward in the first round,’’ Erickson said. “I set him up with my jab and I knew I hurt him in the second. That’s when I knew it was time for him to go.

“I think that fight definitely proves that I’m in the discussion as one of the top up and comers in the sport, but I don’t feel any pressure. I’m back in the gym on Monday.

“I want to be undisputed champion. I want all of the belts. Give me the Charlos, Julian Williams, any of them.

“I’ll take whoever is in front of me next, but those names and put them in bold letters and you know I’ll be front and center for that Charlo-Williams fight.”

The SHOWTIME CHAMPIONSHIP BOXING doubleheader and SHOWTIME INTERNATIONAL telecast will re-air on Monday, Dec. 12, 10 p.m. ET/PT on SHOWTIME EXTREME. The fights were promoted by Ringstar Sports and TGB Promotions and sponsored by Corona.